1. Field of the Invention
The field of the invention relates to luer connector assemblies, and methods for manufacturing such assemblies.
2. Brief Description of the Prior Art
Generally speaking, a hypodermic syringe consists of a cylindrical barrel, most commonly made of thermoplastic material or glass, with a distal end adapted to be connected to a hypodermic needle and a proximal end adapted to receive a stopper and plunger rod assembly. One of the purposes of the stopper is to provide a relatively air tight seal between itself and the syringe barrel so that movement of the stopper up and down the barrel will cause fluids to be drawn into or forced out of the syringe through the distal end. The stopper is moved along the syringe barrel by applying axial force on a rigid plunger rod which is connected to the stopper and is sufficiently long to be accessible outside of the barrel.
Hypodermic needle assemblies, typically including a cannula and a hub, are often times removably attached to syringes for performing a variety of tasks such as the delivery of medication into patients and into devices, and for withdrawing fluid samples from patients and from fluid sources. Usually, the hub of the hypodermic needle assembly has a tapered interior surface adapted to engage the tapered tip of the syringe barrel so that the two components are joined in a frictional interference fit. The tapered syringe tip and the complementary tapered receptacle in the hub are referred to as standard luer fittings. A wide variety of other devices such as stopcocks and tubing sets have standard luer fittings which allow them to be engaged to a syringe tip.
It is important that the frictional fit between the syringe tip and the needle hub or other device is strong enough to prevent accidental disengagement caused by the fluid pressures within the syringe and/or other factors. If the syringe tip becomes disengaged from the other fluid delivery means, medications, blood or other fluids will be lost and there is also potential for contamination of the fluid.
To improve the strength of the interference fit between the syringe tip and the fluid delivery device, such as a hypodermic needle, many prior art devices, such as a hypodermic syringe, provide a circular internally threaded receptacle which is concentric to and larger than the luer tip of the syringe barrel. The hypodermic needle or other fitting used with this type of syringe has wings projecting radially outwardly from the base of the needle hub so that the needle hub may be placed on the syringe tip and rotated in a clockwise direction until the hub wings engage the threads at the syringe tip and pull the needle hub into tight frictional engagement with the syringe tip. This type of fitting is commonly referred to as a luer lock. With a plastic syringe barrel the threaded luer lock collar can be molded integrally with the syringe barrel as taught in U.S. Pat. No. 3,402,713 to Senkowski et al. When using a glass syringe barrel the threaded collar is usually made of a relatively expensive metal part which is chrome plated and attached to the glass syringe. Such a device is taught in U.S. Pat. No. 2,711,171 to Dunnican. The type of device taught by Dunnican is commonly found on reusable glass syringes. However, its relative expense makes it impractical for a disposable syringe assembly.
It is known to blast the tip of a glass syringe with abrasive particles, such as aluminum oxide beads or sand, to increase the roughness of the tip and, therefore, the strength of the frictional interference fit between the syringe tip and the needle hub. The roughened surface also is believed to be helpful in the event that liquid is accidentally deposited on the syringe tip, because the roughened surface is better able to break through the liquid film as the needle hub is engaged thereon. A disadvantage of abrasive blasting a syringe tip to obtain a roughened surface is that the debris created by the blasting process must be thoroughly and completely removed from the syringe barrel. This cleanup operation is an expensive secondary operation which is required because of the medical uses most syringes are placed in.
U.S. Pat. No. 5,312,377 discloses male and female luer members that are comprised of soft, resilient, elastomeric materials. When coupled, the outer periphery of the female luer member conforms to the threads of the luer lock collar of the male luer member. Stiffening inserts may be encapsulated within the luer members using a process referred to as insert molding.
The syringe tip may alternatively be coated, as disclosed in U.S. Pat. No. 4,589,871 to increase the roughness of the syringe tip. Texturing of the male and female portions of the luer connector to improve retention is disclosed in U.S. Pat. Nos. 5,851,201 and 6,217,560 B1.
Various mechanical locking features have been proposed for coupling syringe tips and needle hubs. U.S. Pat. Nos. 2,764,978 and 2,902,995 disclose examples of such locking or detent features. U.S. Pat. No. 4,040,421 discloses a needle hub having an internal bead that forms a depression in a boss surface on the syringe, thereby supplementing the interference fit. U.S. Pat. Nos. 4,369,781 and 4,676,530 disclose locking members such as lock washers used to enhance the retention of male and female luer fittings.